A database has a Managers table and an Employees table. The Employees table references the Managers table using a Foreign Key. The database is set to ON DELETE CASCADE. (a) Explain what ON DELETE CASCADE means in simple English. (b) If you delete one Manager from the database, what will automatically happen to all Emgim2. (b) If you delete one Manager from the database, what will automatically happen to all Employees under that manager? (c) Explain why this is very dangerous in a real banking system. What is the best practice and how does it fix this danger?

(a) Meaning of ON DELETE CASCADE:

ON DELETE CASCADE is a foreign key constraint action in relational database management systems. It specifies that if a record in the parent table (referenced table) is deleted, all corresponding records in the child table (referencing table) that depend on that parent record will automatically be deleted as well.

(b) Consequence of Deleting a Manager:

If you delete one manager from the Managers table, all employee records in the Employees table that reference that manager via the foreign key will be automatically and permanently removed from the database.

(c) Danger in a Banking System and Best Practices:

Why it is dangerous in a real banking system:

    
• Loss of Audit Trail: Banking systems strictly require immutable financial records and audit trails. Automatic cascading deletions physically destroy historical data, ledger associations, and transaction histories.
    
• Accidental Mass Destruction: Deleting a single parent record (such as a Manager, Account, or Branch) could accidentally wipe out hundreds or thousands of dependent customer or employee records without warning or confirmation.
    
• Security and Regulatory Non-Compliance: Critical banking data disappearing automatically makes fraud detection impossible, violating statutory legal and financial compliance rules.

Best Practice and Solution:

    
• ON DELETE RESTRICT / NO ACTION: Change the foreign key constraint to RESTRICT or NO ACTION. This prevents the deletion of a parent record as long as dependent child records exist, throwing an error and requiring the administrator to manually reassign or archive dependent data first.
    
• Soft Deletes (Logical Deletion): Instead of physically running a DELETE command, use a flag column (e.g., is_active = FALSE or deleted_at = TIMESTAMP) to mark records as inactive while preserving all historical data for auditing and reporting.